The ROM programmer on display, with an OLED screen attached

Relatively Universal ROM Programmer Makes Retro Tech Hacking Accessible

There’s treasures hidden in old technology, and you deserve to be able to revive it. Whether it’s old personal computer platforms, vending machines, robot arms, or educational kits based on retro platforms, you will need to work with parallel EEPROM chips at some point. [Anders Nielsen] was about to do just that, when he found out that a TL866, a commonly used programmer kit for such ROMs, would cost entire $70 – significantly raising the budget of any parallel ROM-involving hacking. After months of work, he is happy to bring us a project – the Relatively Universal ROM Programmer, an open-source parallel ROM programmer board that you can easily assemble or buy.

Designed in the Arduino shield format, there’s a lot of care and love put into making this board as universal as reasonably possible, so that it fits any of the old flash chips you might want to flash – whether it’s an old UV-erasable ROM that wants a voltage up to 30 V to be written, or the newer 5 V-friendly chips. You can use ICs with pin count from 24 to 32 pins, it’s straightforward to use a ZIF socket with this board, there’s LED indication and silkscreen markings so that you can see and tweak the programming process, and it’s masterfully optimized for automated assembly.

You can breadboard this programmer platform as we’ve previously covered, you can assemble our own boards using the open-source files, and if you don’t want to do either, you can buy the assembled boards from [Anders Nielsen] too! The software is currently work in progress, since that’s part of the secret sauce that makes the $70 programmers tick. You do need to adjust the programming voltage manually, but that can be later improved with a small hardware fix. In total, if you just want to program a few ROM chips, this board saves you a fair bit of money.

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A Low-Cost ROM Programmer With An AI Twist

There are 0x10 ways to look at ROM programmers: they’re either relatively low-cost tools that let you quickly get about the business of programming vintage ROMs and get back to your retrocomputing activities, or they’re egregiously overpriced on a per-use basis. [Anders Nielsen] seems to land in the latter camp, firmly enough that he not only designed a dedicated ROM programmer for his 65uino ecosystem, but also suffered the indignities of enlisting ChatGPT to “help” him program the thing.

We’ll explain. [Anders]’ 65uino project has been going on for a while, with low-cost ROM programming only the latest effort. To his way of thinking, a $60 or $70 programmer might just be a significant barrier to those trying to break into retrocomputing, and besides, he seems to be more about the journey than the destination. He recently tackled the problem of generating the right programming voltages; here he turns his attention to putting that to work programming vintage ROMs like the W27C512.

Doing so with a 6502-based Arduino-compatible microcontroller requires some silicon calisthenics, including a trio of shift registers to do the addressing using a minimum of GPIO. As for the ChatGPT part, [Anders] thought asking the chatbot to help write some of the code would be a great way to increase his productivity. We thought so too, at least once, and like us, [Anders] concluded that while perhaps helpful in a broad sense, the amount of work you put into checking a chatbot’s work probably exceeds the work saved. But no matter, because in the end the code and the hardware came together to create a prototype ROM programmer for only about $10 worth of parts.

True, the resulting circuit is a bit complex, at least on a breadboard. It should clean up nicely for an eventual PCB version, though, one that plugs right into the 65uino board or even other microcontrollers. Either way, it could make creating custom ROMs for the 65uino a little more accessible.

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Generator Control Panel Unlocked With Reverse Engineering Heroics

Scoring an interesting bit of old gear on the second-hand market is always a bit of a thrill — right up to the point where you realize the previous owner set some kind of security code on it. Then it becomes a whole big thing to figure out, to the point of blunting the dopamine hit you got from the original purchase.

Fear not, though, because there’s dopamine aplenty if you can copy what [Buy it Fix it] did to decode the PIN on a used generator control panel. The panel appears to be from a marine generator, and while it powered up fine, the menu used to change the generator’s configuration options is locked by a four-digit PIN. The manufacturer will reset it, but that requires sending it back and paying a fee, probably considerable given the industrial nature of the gear.

Instead of paying up, [Buy it Fix it] decided to look for a memory chip that might store the PIN. He identified a likely suspect, a 24LC08B 8-Kb serial EEPROM, and popped it off to read its contents. Nothing was immediately obvious, but blanking the chip and reinstalling it cleared the PIN, so he at least knew it was stored on the chip. Many rounds of soldering and desoldering the chip followed, blanking out small sections of memory each time until the PIN was located. The video below edits out a lot of the rework, but gives the overall gist of the hack.

To be honest, we’re not sure if the amount of work [Buy it Fix it] put into this was less than taking a couple of hours to punch in PINs and brute-force it. Then again, if he hadn’t done the reverse engineering he wouldn’t have stumbled upon where the generator parameters like running time and power figures were stored. And it’s not really his style, either; we’ve seen him perform similar heroics on everything from tractors to solar inverters, after all.

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Fixing A Tractor Dashboard From Over 10,000 Miles Away

[BuyItFixIt] is well known as a dab hand at, well, fixing things… and presumably buying them, too. Recently, they received an email calling for help of the former kind. One of their Australian viewers owned the same model of tractor, but with a dead digital dash. Thankfully, help was at hand!

The problem turned out to be due to a dead EEPROM on the Australian tractor. In contrast, [BuyItFixIt] had a perfectly working dashboard on their tractor. Thus, they set about disassembling the dash and dumping the EEPROM to try and sort the stricken farm implement. This posed some risk of ending up with two dead dashboards, necessitating a careful hand. In any case, the Case tractor had a fairly simple dash with a majority of through-hole components, making it fairly easy to work with. The Microchip 93LC46B chip was in a DIP package, and was removed with the aid of some low-melting point solder in short order. The contents of the EEPROM were then dumped to a file using a XGecu T48 programmer.

With the file sent off via email, the Australian tractor owner flashed a fresh EEPROM and reinstalled it in their cluster. They were greeted with success, with the only complication being that the hours reading on the cluster had to be corrected to match the previous reading on their machine.

It’s a fairly simple story of fixing an embedded system, but it’s an educational one. It also comes with a deeper dive into how the CASE dashboard works. Just about anyone with basic electronic skills could pull this off and save an entire tractor in the process. It’s great to see these jobs documented so that we can all learn useful basic skills like these. Video after the break.

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Erasing EEPROMs Isn’t Always As Easy As It Seems

When is 14 volts not actually 14 volts? Given [Anders Nielsen]’s recent struggles with erasing an old-school EEPROM, it’s when you really need it that things tend to go pear-shaped.

A little background is perhaps in order. [Anders] is working on a scratch-built programmer for ROMs to complement his 65uino project, which puts a complete 6502 computer into the footprint of an Arduino Uno. He wisely started the ROM programmer project at the beginning, which was to generate the correct voltages for programming. This turned out to be not as easy as you might think thanks to the solderless breadboard’s parasitic effects on the MIC2288 switching boost regulator he chose.

The video below is a continuation of the programmer build, which ends up being just as fraught as the first part. Being able to generate the programming voltages is one thing; getting them onto the right pins at the right time using nothing but the 5-volt GPIOs on a microcontroller is another. In true retro fashion, [Anders] tackled that problem with a pair of small-signal transistors, which seemed to work once the resistor values were sorted, at least when applying a 12-volt signal intended to show the ROM’s hard-coded manufacturer ID on the data bus.

But erasing the ROM, which requires 14 volts while the chip enable line is held high for 100 ms, proved a little trickier. Despite multiple tries, the ROM wouldn’t erase thanks to the 14-volt rail being dragged down to around 9 volts. [Anders] fixed that with a new base resistor on the driver, to increase the current and keep the voltage up where it needs to be. Just goes to show you that the data sheets don’t always tell the whole story.

We’ve been enjoying the unfolding story of this programmer, and we’re looking forward to the next installment.

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How Do You Test If An EEPROM Can Hold Data For 100 Years?

Data retention is a funny thing. Atmel will gladly tell you that the flash memory in an ATmega32A will retain its data for 100 years at room temperature. Microchip says its EEPROMs will retain data for over 200 years. And yet, humanity has barely had a good grasp on electricity for that long. Heck, the silicon chip itself was only invented in 1958. EEPROMs and flash storage are altogether younger themselves.

How can these manufacturers make such wild claims when there’s no way they could have tested their parts for such long periods of time? Are they just betting on the fact you won’t be around to chastise them in 2216 when your project suddenly fails due to bit rot.

Well, actually, there’s a very scientific answer. Enter the practice of accelerated wear testing.

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Switching Converter For EEPROM Programmer Taxes Solderless Breadboard

We all know that solderless breadboards have their limitations. All that stray capacitance can play hell with circuits, especially high-speed stuff, but they’re so darn useful that avoiding them in favor of some other prototyping method can be really hard. So we often just forge ahead, plugging in our parts and hoping for the best

A recent veteran of the breadboard battle is [Anders Nielsen], who kicked off a new project by prototyping this high-voltage boost converter on a breadboard, with mixed results. The project is a scratch-built programmer for old-school ROM chips, a task normally farmed out to a dedicated programmer, but where’s the sport in that? Besides, this is the future, and generating the 12 to 14 volts needed should be a snap. And it would be, except for the fact that his chosen chip, a MIC2288 switching boost regulator, is only available in an SMD package. Getting the chip and a few other SMD support components onto breadboard-compatible breakouts proved to be challenging, and getting it working once it was there was even more work.

A lot of the trouble was down to simple breadboarding errors, but the big problem was the input capacitance, which [Anders] had to fiddle with quite a bit to get the converter to 14 volts. The current maxes out at about 25 mA before the voltage starts dropping, which just might be enough to burn those old chips, so we’ll call this a provisional win and see what happens when he builds the rest of the programmer.

[Anders]’ experience here raises a good question: what’s the best way to prototype using fussy SMD components? PCBs are cheap enough that it’s tempting to go straight to one, but swapping parts in and out like he had to do here to get everything just right would be much harder that way. We’re not sure we know the answer, but we’re pretty sure we’ll hear your thoughts on that in the comments section.

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